1. Field of the Invention
This invention relates to a temperature measurement device which uses as its temperature sensing element a quartz resonator which can measure a wide range of temperatures from extremely low temperature to room temperature at high resolution.
2. Prior Art Statement
In equipment which uses or controls various physical phenomena which occur in the extremely low temperature region, temperature sensors which are able to measure temperatures in the range of, for example, from several degrees K. to 300 K. (-269.degree. C. to 25.degree. C.) with high resolution and high precision are vital.
Conventional temperature sensors include sensors which employ as their temperature sensing element platinum, the semiconductor material germanium, carbon or other materials whose resistance values change with temperature, along with thermocouples which employ thermoelectromotive force.
However, while the known temperature sensors described above are able to measure temperature changes at relatively high precision over certain specific temperature ranges, little variation is exhibited over other temperature ranges, making the measurement of temperature over the entire range from extremely low temperature to room temperature difficult. For example, as shown by the line "a" on FIG. 1, the change in resistance of a temperature sensor which uses platinum as its temperature sensing element is small in the extremely low temperature region, so it is difficult to measure temperature changes in that region with high resolution. On the other hand, as shown by the line "b" on FIG. 1, a temperature sensor which uses germanium, carbon or another semiconductor as its temperature sensing element demonstrates a large change in resistance due to temperature at extremely low temperature so it is able to measure temperatures in this region at high resolution, but in the region from 15 K. to 300 K., its change in resistance decreases rapidly so the resolution of temperature measurement drops in this region.
To remedy this situation, the conventional method of measuring temperatures at high resolution and good precision over a wide range from extremely low temperature to room temperature is to use a combination of several temperature sensors of different temperature measurement range characteristics, so depending on the temperature range to be measured, the device can be switched to the temperature sensor which is able to measure that temperature range at high precision, and then carry out the temperature measurement.
However, this method of carrying out temperature measurement by using several different types of temperature sensors in tandem causes problems in that the temperature sensor construction and measurement process become complex and the characteristics of the temperature sensing elements are different, increasing dispersion in measurement characteristics.
In the case of temperature sensors which employ variation in resistance, power supply circuits able to supply an accurate constant current are required, and temperature sensors which employ thermocouples must always have a set reference zero point (freezing point).
Furthermore, these temperature sensors normally comprise a temperature sensing element (measurement section) and a main measurement unit (computation and display section), and particularly in the measurement of temperatures in the extremely low temperature region, the temperature sensing element is placed in the region of extremely low temperature and electrically connected by wire to a main measurement unit placed outside of this region. However, this requires that a wire with one end at room temperature is inserted into a region of extremely low temperature, causing an inflow or outflow of heat to the region of extremely low temperature, and thus is not preferable.
In Japanese Patent Public Disclosure No. SHO 63(1988)-50646, a temperature measurement device which uses as its temperature sensing element a quartz resonator and can remotely measure the temperature of a room-temperature region to be measured was disclosed, but in that publication, measurement of extremely low temperatures was not touched upon at all.
The object of this invention is to provide a temperature measurement device which is able to accurately measure the temperature of a region to be measured without disturbing that region measured by outflow or inflow of heat.